Furuncle/Carbuncle

Synonyms

Boil.

Epidemiology

10–20% of the population are carriers of Staphylococcus.

Definition

Furuncle: deep follicular infection with abscess formation caused by Staphylococcus aureus or mixed infections.
Carbuncle: conglomerate of multiple confluent deep follicular infections (furuncles), sometimes with multiple fistular openings.

Aetiology & Pathogenesis

Infection either spreads via autoinoculation (from nose or throat) or exogenous, site of entry is the follicle ostium; transfer from nostrils, armpits, groin or natal cleft. It may be transferred to other sites from the nostrils via the finger nails.

Signs & Symptoms

Initially firm nodule, then fluctuant abscess with central necrotic plug, often oedema, lymphangitis, lymphadenitis, spontaneous rupture and drainage, ulceration, later yellow-brown crusts, often painful.

Localisation

All hair-bearing regions, often neck, face, axillae, or buttocks or back of upper shins.

Classification

None.

Laboratory & other workups

In case of carbuncle, check leucocytes, CRP, glucose.

Dermatopathology

Severe inflammation with accumulation of neutrophils and macrophages within and in the surrounding the follicular canal with distruction of follicle and dermal collagen and other adnexal structures. In carbuncle, fistular structures on serial sections.

Course

Painful and highly inflammatory course with spontaneous rupture of central follicular opening with masses of pus.

Complications

Septic course with hematogenous spread and bacterial involvement of heart valves, joints or kidneys possible. In mid-face, risk of cavernous sinus thrombosis.

Diagnosis

Clinical feature and course.

Differential diagnosis

Deep Trichophyton infections (beard), hidradenitis suppurativa (axillae), necrotic herpes simplex, localized panniculitis, dracunculosis.

Prevention & Therapy

Incision when fluctuation starts and continuous drainage with tamponade. Bed rest, elevation of involved area (face: talking, chewing forbidden).
Systemic antibiotics for mid-face lesions and high-risk patients: penicillinase-resistant penicillins (oxacillin). Culture and sensitivity, since resistance is common and adjustments needed.
Topical: no mechanical manipulation, wet antimicrobial dressings (chlorhexidine, povidone-iodine etc).

2.2.5 Furuncle/Carbuncle